joshua christy windsor school of medicine, ms-4 may 25, 2018 · pathophysiology = lesion of the...

Joshua Christy

Windsor School of Medicine, MS-4

May 25, 2018

▪ Pupillary Light Reflex

▪ Marcus Gun Pupil

▪ Accommodation Reflex

▪ Argyll Robertson Pupil

▪ Oculomotor Nerve Palsy

▪ Anisocoria

▪ Adie’s Tonic Pupil

▪ Horner’s Syndrome

▪ Saccadic Eye Movements

▪ Progressive Supranuclear Palsy

▪ Nystagmus

▪ Central Vs. Peripheral

▪ Downbeat

▪ Upbeat

▪ Torsional

▪ Vertigo

▪ Shine light in one eye

▪ ipsilateral constriction = direct response

▪ contralateral constriction = consensual response

▪ Why both eyes react?

▪ Light in one eye will reach both Edinger-Westphal nuclei

1

• Also known as Relative Afferent Pupillary Defect

• Shine light in affected eye:

• No direct or consensual response

• Mechanism:

• Reduction in afferent input reaching the

pretectum in the midbrain

• Potential cause:

• Optic nerve lesion

• https://www.youtube.com/watch?v=ToFIadG5tqM

Visual

Stimulus

Lateral

Geniculate

Nucleus

Thalamus

Occipital

Cortex

1

2

3

Edinger-

Westphal

Nucleus

Oculomotor

Nerve

Ciliary

Ganglion

Ciliary

Muscle of

Iris

4

56

7

▪ Seen with syphilis and diabetic neuropathy

▪ Pathophysiology:

▪ lesion of dorsal reflex fibers from the Edinger-Westphal nucleus responsible for the light reflex.

▪ Signs:

▪ Bilateral small pupils

▪ Accommodation is normal

▪ ventral reflex fibers are unharmed

▪ Dilation of pupil immediately after constriction

2

Optic Light Reflex will

still be present

3

• Pathophysiology: damage to cranial nerve III

• Damages light reflex:

• Fixed dilated pupil and poor vision in affected eye

• If shining light in one eye causes contralateral

dilation:

• suggests an optic neuropathy in initial eye

• Causes ptosis:

• deficit in adduction, depression, or elevation of the

eye

• Cranial nerve III supplies the upper eyelid

• Affects extraocular muscles:

• Classic position: down and out

• Most common cause of palsy:

• vascular insufficiency from hypertension or

atherosclerosis

▪ Asymmetric pupil sizes

▪ Need to compare inequality in light and dark

▪ In light

▪ LARGER pupil has PARASYMPATHETIC abnormality

▪ Causes = Adie’s Tonic Pupil, 3rd nerve palsy, cocaine

▪ In dark

▪ SMALLER pupil has SYMPATHETIC dysfunction

▪ Most common cause = Horner’s Syndrome

▪ Damage to the parasympathetic ciliary ganglion

▪ No response to light, will have light-near dissociation

▪ Pupil is initially large, exhibits accommodation

▪ Redilates slowly after constriction

▪ Pathophysiology: Damage to sympathetic trunk

▪ Signs seen on affected side:

▪ Miosis: constricted pupil

▪ Ptosis: droopy weak eyelid

▪ Anhidrosis: decreased sweating

▪ Causes:

▪ Idiopathic

▪ Pancoast tumor (apical lung)

▪ Internal carotid dissection

▪ Brainstem stroke

▪ Neck trauma

▪ Quick ballistic movement that allows fixation from one target to another

▪ Conjugate eye movement:

▪ Both eyes move in the same direction

▪ Once initiated, cannot be stopped

▪ https://www.youtube.com/watch?v=TNooKldf-gw

Visual

Stimulus

Lateral

Geniculate

Nucleus

Thalamus

Occipital

Cortex

Frontal

Eye

Fields

Superior

Colliculus

Midbrain

Motor

Neurons

of VI

Burst Cells

in PPRF

Pons

Burst Cells

in riMLF

Omnipause

neurons in

rip Nucleus

1

2

3

4

5

6

7

-

+

8Midbrain

Pons

MLF &

Motor

Neuron

3 9

Visual

Stimulus

Lateral

Geniculate

Nucleus

Thalamus

Occipital

Cortex

Frontal

Eye

Fields

Superior

Colliculus

Midbrain

Burst Cells

in PPRF

Pons

Burst Cells

in riMLF

Omnipause

neurons in

rip Nucleus

1

2

3

4

5

6

-

+

7

Midbrain

Pons

Motor

Neurons

of VI

8

MLF &

Motor

Neuron

3 9

▪ Pathophysiology = Lesion of the midbrain

▪ Rostral Interstitial Nucleus of the MLF

▪ Presents with gait disturbance - leads to falls

▪ Supranuclear Ophthalmoplegia = Weakness in eye muscles over time

▪ First ocular symptoms = Vertical Saccades

▪ Round the House Sign

▪ Slow Saccadic Velocity

▪ Hypometric- undershoot or do not reach target

▪ Square Wave Jerks- Eyes drift off target, and a quick saccade pulls the eyes into neutral position

▪ Bradykinesia of the neck and upper trunk

▪ Cognitive impairment

▪ Diagnostic Test = CT and MRI

▪ generalized and brainstem atrophy especially in midbrain

▪ Management = Physical therapy for postural instability and falls

▪ Mirror prism lenses if severe limitation of extraocular movements

▪ Pharmacology = Levodopa can be used to diagnose

▪ Not enough data to use drugs as treatment

▪ Prognosis = 6-9 years

▪ Repetitive, uncontrolled eye movements▪ side to side

▪ up and down

▪ circular pattern

▪ Semicircular canal = push-pull mechanism▪ Angular movement of the head:

▪ maximally activate one canal

▪ maximally inhibit the other canal

▪ Canal is excited by head motion towards the canal, in the appropriate plane▪ Posterior canal = excited with neck EXTENSION

▪ Anterior canal = excited with neck FLEXION

▪ Central vestibular nystagmus

▪ From the vestibular nuclei and neural pathways beyond

▪ Peripheral vestibular nystagmus

▪ labyrinth and semicircular canals of the inner ear

▪ Nystagmus can present as Downbeat, Upbeat, and/or Torsional

https://www.youtube.com/watch?v=d0Kfr2mF0Bg

▪ Unopposed action from ANTERIOR semicircular canal

▪ Pathophysiology:

▪ lesion in the medulla = where posterior semicircular canal tracts run

▪ cerebellar flocculus lesion = removes a tonic inhibition of upward vestibular eye movements

▪ Downbeat = due to saccade that tries to correct it

▪ Causes:

▪ Chiari Type 1 = cerebellar tonsils below the level of foramen magnum

▪ Demyelinating Multiple Sclerosis.

▪ Drugs = lithium and anticonvulsants (phenytoin or carbamazepine)

▪ Presents with:▪ blurred vision

▪ oscillopsia = illusion that the environment is moving while moving head

▪ If oscillopsia is provoked by neck extension or rotation:▪ Consider Arnold Chiari

▪ Otherwise, consider MS or drug induced nystagmus

▪ Ask patient to gaze downward will increase nystagmus

▪ Treatment = dalfampyridine▪ K+ channel blocker which increases action potential

https://www.youtube.com/watch?v=7MqyHgozqH0

▪ Pathophysiology:

▪ Unopposed action of POSTERIOR semicircular canals

▪ Most common causes:

▪ strokes to the medial brainstem

▪ degeneration to the cerebellum

▪ Why = projections of anterior semicircular canals travel through cerebellum and medial brainstem

▪ Presents with possible blurred vision

▪ Ask patient to look upward, will increase upward nystagmus

▪ No proven treatment

▪ some benefit with dalfampyridine

▪ Fast phase intorsion or extorsion that is conjugate and symmetric

▪ If purely torsional:▪ Localized to the brainstem

▪ Contralateral to the fast phase

▪ Ocular tilt reaction direction = ipsi-lesional

▪ If torsional with a downward or an upward component:▪ Localized to the midbrain

▪ Ocular tilt reaction direction = contralateral to lesion

▪ Causes:▪ Stroke

▪ Demyelinating disease

▪ Chiari malformation

▪ https://www.youtube.com/watch?v=Av8nifL5XDg

▪ Symptoms:

▪ Severe vertigo

▪ Tinnitus

▪ hearing loss

▪ Clinical Exam = fixation of vision, will decrease nystagmus.

▪ Diagnosis = Dix-Halpike

▪ Treatment = Epley Maneuver

• Dependent ear is facedown

• Develop a torsional upbeating nystagmus

Central Peripheral

Purely, vertical, horizontal or

torsional

Combined horizontal and

torsional or vertical and

torsional

Fast beat towards side of lesion Fast beat away from lesion

Not relieved by gaze fixation Relieved by gaze fixation

▪ “Adie Tonic Pupil.” American Academy of Ophthalmology, www.aao.org/bcscsnippetdetail.aspx?id=1af235eb-71a5-497f-8fac-308c9ea3a0eb.

▪ Barton, Jason JS. “Overview of Nystagmus.” UpToDate, June 2017, www.uptodate.com/contents/overview-of-nystagmus?search=Saccadic%2BEye%2BMovements&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1.

▪ “Chapter 9.” Chapter 14, www.opt.indiana.edu/v665/CD/CD_Version/CH9/CH9.HTM#Horiz.%20Vert.

▪ Factor, Stewart A, and Christine Doss Esper. “Progressive Supranuclear Palsy (PSP).” Edited by Howard I Hurtig and April F Eichler, UpToDate, 31 Jan. 2018, www.uptodate.com/contents/progressive-supranuclear-palsy-psp-clinical-features-and-diagnosis?search=progressive%2Bsupranuclear%2Bpalsy%2Badult&source=search_result&selectedTitle=1~35&usage_type=default&display_rank=1.

▪ Geib , Douglas. “The Detailed Neurologic Examination in Adults.” UpToDate, Sept. 2012, www.uptodate.com/contents/the-detailed-neurologic-examination-in-adults?search=marcus%2Bgunn%2Bpupil&source=search_result&selectedTitle=1~35&usage_type=default&display_rank=1.

▪ Kedar, Sachin, et al. “Approach to Patient with Anisocoria .” UpToDate, July 2017, www.uptodate.com/contents/approach-to-the-patient-with-anisocoria.

▪ Kedar, Sachin, et al. “Horner Syndrome.” UpToDate, 14 July 2015, www.uptodate.com/contents/horner-syndrome?topicRef=5243.

▪ Lee, Andrew. “Third Cranial Nerve Oculomotor Palsy in Adults.” UpToDate, 19 June 2017, www.uptodate.com/contents/third-cranial-nerve-oculomotor-nerve-palsy-in-adults?search=oculomotor%2Bnerve%2Bpalsy&source=search_result&selectedTitle=1~58&usage_type=default&display_rank=1.

▪ Lee, Andrew. “Tonic Pupil.” UpToDate, 2015 Oct. 19AD, www.uptodate.com/contents/tonic-pupil?search=Pupil&source=search_result&selectedTitle=3~131&usage_type=default&display_rank=3.

▪ Liu, Grant, et al. Neuro-Opthalmology Diagnosis and Management . 2nd ed., Saunders Elsevier , 2010.

▪ Martin, et al. “Alterations of Eye Movement Control in Neurodegenerative Movement Disorders.” International Scholarly Research Notices, Hindawi, 18 May 2014, www.hindawi.com/journals/joph/2014/658243/.

▪ Olivier A Coubard, et al. Educating the Blind Brain: A Panorama of Neural Bases of Vision and of Training Programs in Organic Neurovisual Deficits. Dec. 2014, www.researchgate.net/figure/Organization-of-cerebral-structures-involved-in-the-control-of-eye-movements_fig2_270004107.

▪ “Peripheral Vestibular Nystagmus.” American Academy of Opthalmology , www.aao.org/bcscsnippetdetail.aspx?id=d20f8ad8-845e-46fc-b7ed-7d00216c2726https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2586990/.

▪ “Pupillary Responses.” Fundoscopic (Ophthalmoscopic) Exam | Stanford Medicine 25 | Stanford Medicine, stanfordmedicine25.stanford.edu/the25/pupillary.html.

▪ Purves, Dale. “Neural Control of Saccadic Eye Movements.” Advances in Pediatrics., U.S. National Library of Medicine, 1 Jan. 1970, www.ncbi.nlm.nih.gov/books/NBK10992/.

▪ Serra, Alessandro, et al. “Diagnosing Disconjugate Eye Movements.” Advances in Pediatrics., U.S. National Library of Medicine, 7 Oct. 2008, www.ncbi.nlm.nih.gov/pmc/articles/PMC2586990/.

▪ Termsarasab, Pichet, et al. “The Diagnostic Value of Saccades in Movement Disorder Patients: a Practical Guide and Review.” Journal of Clinical Movement Disorders, BioMedCentral, 15 Oct. 2015, clinicalmovementdisorders.biomedcentral.com/articles/10.1186/s40734-015-0025-4.